The present invention relates to a stacked, high-packaging-density and multi-function semiconductor device, wherein semiconductor layers are stacked one on top of another through an insulation layer and a local conductive layer.
A conventional semiconductor device of the type contemplated by the present invention is shown in FIG. 1, wherein reference numeral 1 is a silicon substrate, 2 is an integrated circuit element formed on the silicon substrate, 3 is an integrated circuit element formed on an overlying semiconductor, 4 is an integrated circuit element formed on another overlying semiconductor, 5 is a semiconductor layer having the topmost integrated circuit, as well as a circuit element thereof, and 6 is a photoelectric sensor which forms the topmost layer of the device of FIG. 1 and is assembled thereto by face-down bonding. The respective semiconductor layers are stacked one on top of another to form areas that are equal in size to the active region (having no pad) of the substrate semiconductor layer.
In the semiconductor device of FIG. 1, the semiconductor layer 6 forms the fifth layer and works as a photoelectric sensor, the layer 5 forms the fourth layer and functions as a preprocessing circuit or an A-D control circuit, third layer 4 is responsible for image processing and storage, second layer 3 forms a display D-A circuit, and the first layer 2 is an image processing CPU. With such a configuration, the conventional stacked semiconductor device has some technical difficulties with heat dissipation and conduction between each layer and needs improvement in the crystallinity of each semiconductor layer. In addition, the reliability and production yield of the device are low.